Any recommendation on what rate to sample the TPS. The default was 100Hz which seems unnecessarily high

In my experience 50Hz or 25Hz is plenty for TPS. You can probably get away with 10 Hz, but it is possible that in extremely fast throttle angle changes, you will loose detail/resolution in the graph. The lower the Hz you record in, the more time you will be able to hold in the GPX Pro's memory, but the less resolution the graphs will have. If you don't mind downloading to your PC often and you have plenty of disk space to store files, there is not really a reason to record at a low Hz setting. You will have to experiment to find what is best for your needs.

That makes sense and I have a huge amount of storage so that is not an issue. Is there any limitation on the devices ability to dump data on all channels at max rate though (that was my biggest fear)

There is a variable on the main screen called "minuets of memory free". This is a calculated estimation of the minutes of data you can store with the current DAQ settings. If you note the minutes remaining and then turn on or off a channel, or change a channel's hertz, you will notice this number change. You can use this to tell approximately how long you will be able to record with the current settings. If you will need to time a 30 minute session and that number estimates 10 minuets of memory remaining, you will have to dump the data to GPStudio and clear the system's memory, or lower the Hz on one or more channels, or turn off some channels.

I hope this explains how this works.

Actually I was meaning the bandwidth of the chip, memory, etc. At some point you cannot push the data to storage fast enough.

The GPX Pro will record fine with all channels at the maximum sample rate.